1. Field of the Invention
The present invention relates to a communication system using an optical conductor, more specifically a sheet-type optical conductor comprising a sheet-type optical medium containing particles for scattering light, and propagating the light injected from one edge of the medium to the other by scattering it by means of the particles. It also relates to the aforementioned sheet-type optical conductor.
2. Description of the Related Art
Optical conductors comprising an optical medium, such as PMMA (polymethylmethacrylate), that contains particles for scattering light, and propagates the light injected from one edge of the medium to the other by scattering it by means of the particles are known as described, for example, in Japanese Patent Nos. 3162398 and 3184219.
These optical conductors described above propagate the light by scattering it in succession by means of the particles, in addition to the mechanism of the total reflection at the interface between the side edges of the conductor and the surrounding medium (air or cladding layer), so that they have an advantage that a light beam with more uniformly distributed optical power can be obtained at the output edge compared with an optical conductor that propagates the light only by the mechanism of the total reflection. By making use of this advantage, the application of this type of optical conductor to the construction of an optical data bus (sheet bus) is contemplated, in which the optical conductor is formed using a sheet-type optical medium with an input section being attached to one edge of the medium for injecting an optical signal, and a plurality of output sections being attached to the other edge to distribute an input signal to the plurality of output sections as a common signal as described, for example, in U.S. Pat. No. 5,882,475.
Another type of optical data bus is also known as described, for example, in Japanese Unexamined Patent Publication No. 1999-31035, in which the sheet-type optical medium has light diffusing sections attached to the optical input edge of the medium, each corresponding to each of the input sections for the optical signals, and the optical signals, diffused and branched in the diffusing sections, are propagated to the output edge of the medium.
In the optical data bus described in Japanese Unexamined Patent Publication No. 1999-31035, the light diffusing section needs to be formed of a plurality of optical unit devices of 100 μm on each side, and manufacturing of such a diffusing section is regarded as extremely difficult. In addition, formation of the diffusing sections on one edge of the sheet-type optical medium makes it practically impossible to detect light on that side, so that the edge having the diffusing sections is forced to be used solely for inputting light, thus two-way communication through such a sheet-type optical medium is impossible.
The use of the sheet-type optical conductor described in U.S. Pat. No. 5,822,475 allows two-way communication. But it has been impossible heretofore to readily obtain the design parameters for obtaining a desired level of light-extraction efficiency and uniformly distributed optical output power for this type of sheet-type optical conductor. In this connection, certain techniques have been employed in order to obtain a sheet-type optical conductor having desired characteristics, such as that in which a plurality of samples are produced with varied diameters and densities of the particles contained in the optical medium, and an optical conductor having a desired level of light-extraction efficiency and uniformly distributed optical output power is selected from among them, or that in which the design parameters are obtained through large-scale simulations using computers.